In parent application Ser. No. 08/789,408, U.S. Pat. No. 5,957,248, the background of the art for brakes used in association with steel mill cranes was set forth in detail. In that application, adopted fully herein by reference, there was presented in detail a caliper disk brake assembly adapted for substitution of the prior art drum-shoe brake predominantly used for crane hoist drives. It has been found that even though the caliper disk brake of the parent application provided a significant advance over the prior art drum-shoe brakes, a number of improvements can be made to the caliper disk brakes to even further enhance their operation.
It has been found that dust and other contamination may enter the magnetic armature of the prior caliper disk brake and impede full release of the brake, necessitating routine servicing or cleaning of the brake assembly. Moreover, the prior caliper disk brake has provided no visible indication of torque setting, allowing for the possibility that a brake of improper torque may be placed in an application.
It has further been found that the large mass of spring applied armature plates may cause an undesired torque spike upon brake engagement. Such a shock load may contribute to over-stressing of the shaft upon which the brake disk is mounted. Additionally, the existent caliper disk brakes have generally been quite costly to manufacture.
It has further been found that when a caliper disk brake is used on a crane travel drive, it is most desirable to have the brake applied slowly so that the load on the hoist does not swing exceptionally.
It has also been found to be quite important in the design of caliper disk brakes of the type herein that wear adjustment be easily achieved in the field.
It has further important that there be an easy way to monitor the brake wear in the field.
Yet further, it has been found that the life of the coil within the magnet body of a caliper disk brake may be adversely impacted by shock loads experienced when the crane travels over old uneven rails. Accordingly, there is a need to provide for shock absorption in the traveling mechanism.
It has further been found to be desirable to provide for multi-brake calipers on brake assemblies such that the braking operation can be imparted to the disk at uniformly spaced or diametrically opposed positions thereon.